The specific aims of the proposed research are: 1. To directly measure applied forces by the hands to a load lifted from floor to knuckle height, and compare these to predictions by biomechanical models such as DYNALIFT. If necessary, the dynamic model will be supplemented by a static biomechanical model to account for forces on the hands during the pull phase of the lift, namely as the inertia of the load is picked up. 2. To determine the effects of fast and slow lifting speeds and %MAWL on the external forces applied by the hands to the load during the pull phase of lifting from floor to knuckle height. Blocked factorial statistical designs will be used to analyze the effects of absolute weight, %MAWL, and speed of lift on peak forces applied by the hands to the load during the pull phase of lifting from floor to knuckle height. The National Institute of Occupational Safety and Health Lifting Guide (NIOSH, 1981, p. 40) states that "dynamic forces imparted by rapid or jerky motions can multiply the load's effect greatly," and recommends that manual materials handlers lift the load in a smooth and deliberate manner. However, it is suspected that the human operator must lift in a manner which causes peak forces applied by the hands to the load, resulting from a jerking motion to overcome the inertia of the box resting on the ground. Therefore, smooth and controlled lifting may not be a realistic recommendation. The application of knowledge of the peak applied forces is useful for biomechanically reevaluating lifting tasks, and for establishing the point of time in the lift and associated posture when L5/Sl compression and shear forces may limit lifting capacity.